Feedback overhead reduction for precoders under high rank spatial channels

ABSTRACT

Apparatuses, systems, and methods for a wireless device to encode channel state information (CSI), e.g., enhanced type II CSI. A common frequency basis may be selected. Spatial-frequency coefficients, frequency basis related information, and/or spatial basis related information may be determined. At least a portion of the coefficients and/or information may be encoded in a CSI report.

PRIORITY INFORMATION

This application is a continuation of U.S. patent application Ser. No.16/743,459, entitled “Feedback Overhead Reduction for Precoders underHigh Rank Spatial Channels,” filed Jan. 15, 2020, which claims priorityto U.S. provisional patent application Ser. No. 62/797,507, entitled“Feedback Overhead Reduction for Precoders under High Rank SpatialChannels”, filed Jan. 28, 2019, which is hereby incorporated byreference in its entirety as though fully and completely set forthherein. The claims in the instant application are different than thoseof the parent application or other related applications. The Applicanttherefore rescinds any disclaimer of claim scope made in the parentapplication or any predecessor application in relation to the instantapplication. The Examiner is therefore advised that any such previousdisclaimer and the cited references that it was made to avoid, may needto be revisited. Further, any disclaimer made in the instant applicationshould not be read into or against the parent application or otherrelated applications.

FIELD

The present application relates to wireless devices, and moreparticularly to apparatus, systems, and methods for a wireless device toencode channel state information.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. Further,wireless communication technology has evolved from voice-onlycommunications to also include the transmission of data, such asInternet and multimedia content. Enhanced channel state information(CSI) is important to support features such as beam forming andmultiple-in-multiple out (MIMO), including multi-user MIMO (MU-MIMO).However, such enhanced CSI may increase signaling overhead. Thus,improvements in the field are desired.

SUMMARY

Embodiments relate to apparatuses, systems, and methods to performencoding of channel state information (CSI), e.g., enhanced type II CSI.Embodiments may reduce the signaling overhead associated with CSIreporting, e.g., for multiple-in-multiple-out (MIMO), includingmulti-user MIMO (MU-MIMO), communications. In some embodiments, CSI maybe encoded using one or more of: beam splitting, layer puncturing acrossorthogonal layers, and/or randomized subband (SB) compression.

This Summary is intended to provide a brief overview of some of thesubject matter described in this document. Accordingly, it will beappreciated that the above-described features are merely examples andshould not be construed to narrow the scope or spirit of the subjectmatter described herein in any way. Other features, aspects, andadvantages of the subject matter described herein will become apparentfrom the following Detailed Description, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present subject matter can be obtainedwhen the following detailed description of various embodiments isconsidered in conjunction with the following drawings, in which:

FIG. 1 illustrates an example wireless communication system, accordingto some embodiments;

FIG. 2 illustrates a base station (BS) in communication with a userequipment (UE) device, according to some embodiments;

FIG. 3 illustrates an example block diagram of a UE, according to someembodiments;

FIG. 4 illustrates an example block diagram of a BS, according to someembodiments;

FIG. 5 illustrates an example block diagram of cellular communicationcircuitry, according to some embodiments;

FIGS. 6 and 7 illustrate examples of a 5G NR base station (gNB) andassociated network architecture, according to some embodiments;

FIG. 8 illustrates techniques for encoding CSI with reduced overhead,according to some embodiments;

FIG. 9 illustrates an exemplary antenna array layout, according to someembodiments;

FIG. 10 illustrates a table of ports, antenna layouts, and oversamplingrates, according to some embodiments;

FIGS. 11 and 12 illustrate type II CSI precoding, according to someembodiments;

FIGS. 13 and 14 illustrate type II CSI reporting with ranks 1 and 2,according to some embodiments;

FIG. 15 illustrates type II CSI reporting up to rank 4, according tosome embodiments;

FIG. 16 illustrates type II CSI reporting over time, according to someembodiments;

FIG. 17 illustrates type II CSI precoding overhead reduction via beamsplitting, according to some embodiments;

FIG. 18 illustrates type II CSI precoding overhead reduction via beamsplitting over time, according to some embodiments;

FIGS. 19-22 illustrate type II CSI precoding overhead reduction vialayer puncturing across orthogonal layers, according to someembodiments; and

FIG. 23 illustrates type II CSI precoding overhead reduction viarandomized SB compression, according to some embodiments.

While the features described herein may be susceptible to variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the drawings and detaileddescription thereto are not intended to be limiting to the particularform disclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the subject matter as defined by the appended claims.

DETAILED DESCRIPTION Terms

The following is a glossary of terms used in this disclosure:

Memory Medium—Any of various types of non-transitory memory devices orstorage devices. The term “memory medium” is intended to include aninstallation medium, e.g., a CD-ROM, floppy disks, or tape device; acomputer system memory or random access memory such as DRAM, DDR RAM,SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium mayinclude other types of non-transitory memory as well or combinationsthereof. In addition, the memory medium may be located in a firstcomputer system in which the programs are executed, or may be located ina second different computer system which connects to the first computersystem over a network, such as the Internet. In the latter instance, thesecond computer system may provide program instructions to the firstcomputer for execution. The term “memory medium” may include two or morememory mediums which may reside in different locations, e.g., indifferent computer systems that are connected over a network. The memorymedium may store program instructions (e.g., embodied as computerprograms) that may be executed by one or more processors.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical,electromagnetic, or digital signals.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable interconnect. Examples include FPGAs (Field ProgrammableGate Arrays), PLDs (Programmable Logic Devices), FPGAs (FieldProgrammable Object Arrays), and CPLDs (Complex PLDs). The programmablefunction blocks may range from fine grained (combinatorial logic or lookup tables) to coarse grained (arithmetic logic units or processorcores). A programmable hardware element may also be referred to as“reconfigurable logic”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

User Equipment (UE) (or “UE Device”)—any of various types of computersystems devices which are mobile or portable and which performs wirelesscommunications. Examples of UE devices include mobile telephones orsmart phones (e.g., iPhone™, Android™-based phones), portable gamingdevices (e.g., Nintendo DS™ PlayStation Portable™, Gameboy Advance™,iPhone™), laptops, wearable devices (e.g. smart watch, smart glasses),PDAs, portable Internet devices, music players, data storage devices, orother handheld devices, etc. In general, the term “UE” or “UE device”can be broadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication.

Wireless Device—any of various types of computer system devices whichperforms wireless communications. A wireless device can be portable (ormobile) or may be stationary or fixed at a certain location. A UE is anexample of a wireless device.

Communication Device—any of various types of computer systems or devicesthat perform communications, where the communications can be wired orwireless. A communication device can be portable (or mobile) or may bestationary or fixed at a certain location. A wireless device is anexample of a communication device. A UE is another example of acommunication device.

Base Station—The term “Base Station” has the full breadth of itsordinary meaning, and at least includes a wireless communication stationinstalled at a fixed location and used to communicate as part of awireless telephone system or radio system.

Processing Element—refers to various elements or combinations ofelements that are capable of performing a function in a device, such asa user equipment or a cellular network device. Processing elements mayinclude, for example: processors and associated memory, portions orcircuits of individual processor cores, entire processor cores,processor arrays, circuits such as an ASIC (Application SpecificIntegrated Circuit), programmable hardware elements such as a fieldprogrammable gate array (FPGA), as well any of various combinations ofthe above.

Channel—a medium used to convey information from a sender (transmitter)to a receiver. It should be noted that since characteristics of the term“channel” may differ according to different wireless protocols, the term“channel” as used herein may be considered as being used in a mannerthat is consistent with the standard of the type of device withreference to which the term is used. In some standards, channel widthsmay be variable (e.g., depending on device capability, band conditions,etc.). For example, LTE may support scalable channel bandwidths from 1.4MHz to 20 MHz. In contrast, WLAN channels may be 22 MHz wide whileBluetooth channels may be 1 Mhz wide. Other protocols and standards mayinclude different definitions of channels. Furthermore, some standardsmay define and use multiple types of channels, e.g., different channelsfor uplink or downlink and/or different channels for different uses suchas data, control information, etc.

Band—The term “band” has the full breadth of its ordinary meaning, andat least includes a section of spectrum (e.g., radio frequency spectrum)in which channels are used or set aside for the same purpose.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thus,the term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, i.e., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

Approximately—refers to a value that is almost correct or exact. Forexample, approximately may refer to a value that is within 1 to 10percent of the exact (or desired) value. It should be noted, however,that the actual threshold value (or tolerance) may be applicationdependent. For example, in some embodiments, “approximately” may meanwithin 0.1% of some specified or desired value, while in various otherembodiments, the threshold may be, for example, 2%, 3%, 5%, and soforth, as desired or as required by the particular application.

Concurrent—refers to parallel execution or performance, where tasks,processes, or programs are performed in an at least partiallyoverlapping manner. For example, concurrency may be implemented using“strong” or strict parallelism, where tasks are performed (at leastpartially) in parallel on respective computational elements, or using“weak parallelism”, where the tasks are performed in an interleavedmanner, e.g., by time multiplexing of execution threads.

Configured to—Various components may be described as “configured to”perform a task or tasks. In such contexts, “configured to” is a broadrecitation generally meaning “having structure that” performs the taskor tasks during operation. As such, the component can be configured toperform the task even when the component is not currently performingthat task (e.g., a set of electrical conductors may be configured toelectrically connect a module to another module, even when the twomodules are not connected). In some contexts, “configured to” may be abroad recitation of structure generally meaning “having circuitry that”performs the task or tasks during operation. As such, the component canbe configured to perform the task even when the component is notcurrently on. In general, the circuitry that forms the structurecorresponding to “configured to” may include hardware circuits.

Various components may be described as performing a task or tasks, forconvenience in the description. Such descriptions should be interpretedas including the phrase “configured to.” Reciting a component that isconfigured to perform one or more tasks is expressly intended not toinvoke 35 U.S.C. § 112(f) interpretation for that component.

Acronyms

CSI: channel state information

PMI: precoding matrix indicator

RI: rank indicator

CQI: channel quality indicator

UCI: uplink control information

RS: reference signal

DFT: discrete Fourier transform

WB: wideband

SB: subband

SVD: singular value decomposition

FIGS. 1 and 2 —Communication System

FIG. 1 illustrates a simplified example wireless communication system,according to some embodiments. It is noted that the system of FIG. 1 ismerely one example of a possible system, and that features of thisdisclosure may be implemented in any of various systems, as desired.

As shown, the example wireless communication system includes a basestation 102 which communicates over a transmission medium with one ormore user devices 106A, 106B, etc., through 106N. Each of the userdevices may be referred to herein as a “user equipment” (UE). Thus, theuser devices 106 are referred to as UEs or UE devices.

The base station (BS) 102 may be a base transceiver station (BTS) orcell site (a “cellular base station”), and may include hardware thatenables wireless communication with the UEs 106A through 106N.

The communication area (or coverage area) of the base station may bereferred to as a “cell.” The base station 102 and the UEs 106 may beconfigured to communicate over the transmission medium using any ofvarious radio access technologies (RATs), also referred to as wirelesscommunication technologies, or telecommunication standards, such as GSM,UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces),LTE, LTE-Advanced (LTE-A), 5G new radio (5G NR), HSPA, 3GPP2 CDMA2000(e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), etc. Note that if the base station102 is implemented in the context of LTE, it may alternately be referredto as an ‘eNodeB’ or ‘eNB’. Note that if the base station 102 isimplemented in the context of 5G NR, it may alternately be referred toas gNodeB′ or ‘gNB’.

As shown, the base station 102 may also be equipped to communicate witha network 100 (e.g., a core network of a cellular service provider, atelecommunication network such as a public switched telephone network(PSTN), and/or the Internet, among various possibilities). Thus, thebase station 102 may facilitate communication between the user devicesand/or between the user devices and the network 100. In particular, thecellular base station 102 may provide UEs 106 with varioustelecommunication capabilities, such as voice, SMS and/or data services.

Base station 102 and other similar base stations operating according tothe same or a different cellular communication standard may thus beprovided as a network of cells, which may provide continuous or nearlycontinuous overlapping service to UEs 106A-N and similar devices over ageographic area via one or more cellular communication standards.

Thus, while base station 102 may act as a “serving cell” for UEs 106A-Nas illustrated in FIG. 1 , each UE 106 may also be capable of receivingsignals from (and possibly within communication range of) one or moreother cells (which might be provided by other base stations 102B-N),which may be referred to as “neighboring cells”. Such cells may also becapable of facilitating communication between user devices and/orbetween user devices and the network 100. Such cells may include “macro”cells, “micro” cells, “pico” cells, and/or cells which provide any ofvarious other granularities of service area size. Other configurationsare also possible.

In some embodiments, base station 102 may be a next generation basestation, e.g., a 5G New Radio (5G NR) base station, or “gNB”. In someembodiments, a gNB may be connected to a legacy evolved packet core(EPC) network and/or to a NR core (NRC) network. In addition, a gNB cellmay include one or more transition and reception points (TRPs). Inaddition, a UE capable of operating according to 5G NR may be connectedto one or more TRPs within one or more gNBs.

Note that a UE 106 may be capable of communicating using multiplewireless communication standards. For example, the UE 106 may beconfigured to communicate using a wireless networking (e.g., Wi-Fi)and/or peer-to-peer wireless communication protocol (e.g., Bluetooth,Wi-Fi peer-to-peer, etc.) in addition to at least one cellularcommunication protocol (e.g., GSM, UMTS (associated with, for example,WCDMA or TD-SCDMA air interfaces), LTE, LTE-A, 5G NR, HSPA, 3GPP2CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), etc.). The UE 106 may alsoor alternatively be configured to communicate using one or more globalnavigational satellite systems (GNSS, e.g., GPS or GLONASS), one or moremobile television broadcasting standards (e.g., ATSC-M/H), and/or anyother wireless communication protocol, if desired. Other combinations ofwireless communication standards (including more than two wirelesscommunication standards) are also possible.

FIG. 2 illustrates user equipment 106 (e.g., one of the devices 106Athrough 106N) in communication with a base station 102, according tosome embodiments. The UE 106 may be a device with cellular communicationcapability such as a mobile phone, a hand-held device, a computer or atablet, or virtually any type of wireless device.

The UE 106 may include a processor that is configured to execute programinstructions stored in memory. The UE 106 may perform any of the methodembodiments described herein by executing such stored instructions.Alternatively, or in addition, the UE 106 may include a programmablehardware element such as an FPGA (field-programmable gate array) that isconfigured to perform any of the method embodiments described herein, orany portion of any of the method embodiments described herein.

The UE 106 may include one or more antennas for communicating using oneor more wireless communication protocols or technologies. In someembodiments, the UE 106 may be configured to communicate using, forexample, CDMA2000 (1×RTT/1×EV-DO/HRPD/eHRPD) or LTE using a singleshared radio and/or GSM or LTE using the single shared radio. The sharedradio may couple to a single antenna, or may couple to multiple antennas(e.g., for multiple-input, multiple-output or “MIMO”) for performingwireless communications. In general, a radio may include any combinationof a baseband processor, analog RF signal processing circuitry (e.g.,including filters, mixers, oscillators, amplifiers, etc.), or digitalprocessing circuitry (e.g., for digital modulation as well as otherdigital processing). Similarly, the radio may implement one or morereceive and transmit chains using the aforementioned hardware. Forexample, the UE 106 may share one or more parts of a receive and/ortransmit chain between multiple wireless communication technologies,such as those discussed above.

In some embodiments, the UE 106 may include any number of antennas andmay be configured to use the antennas to transmit and/or receivedirectional wireless signals (e.g., beams). Similarly, the BS 102 mayalso include any number of antennas and may be configured to use theantennas to transmit and/or receive directional wireless signals (e.g.,beams). To receive and/or transmit such directional signals, theantennas of the UE 106 and/or BS 102 may be configured to applydifferent “weight” to different antennas. The process of applying thesedifferent weights may be referred to as “precoding”.

In some embodiments, the UE 106 may include separate transmit and/orreceive chains (e.g., including separate antennas and other radiocomponents) for each wireless communication protocol with which it isconfigured to communicate. As a further possibility, the UE 106 mayinclude one or more radios which are shared between multiple wirelesscommunication protocols, and one or more radios which are usedexclusively by a single wireless communication protocol. For example,the UE 106 might include a shared radio for communicating using eitherof LTE or 5G NR (or LTE or 1×RTT or LTE or GSM), and separate radios forcommunicating using each of Wi-Fi and Bluetooth. Other configurationsare also possible.

FIG. 3 —Block Diagram of a UE

FIG. 3 illustrates an example simplified block diagram of acommunication device 106, according to some embodiments. It is notedthat the block diagram of the communication device of FIG. 3 is only oneexample of a possible communication device. According to embodiments,communication device 106 may be a user equipment (UE) device, a mobiledevice or mobile station, a wireless device or wireless station, adesktop computer or computing device, a mobile computing device (e.g., alaptop, notebook, or portable computing device), a tablet and/or acombination of devices, among other devices. As shown, the communicationdevice 106 may include a set of components 300 configured to performcore functions. For example, this set of components may be implementedas a system on chip (SOC), which may include portions for variouspurposes. Alternatively, this set of components 300 may be implementedas separate components or groups of components for the various purposes.The set of components 300 may be coupled (e.g., communicatively;directly or indirectly) to various other circuits of the communicationdevice 106.

For example, the communication device 106 may include various types ofmemory (e.g., including NAND flash 310), an input/output interface suchas connector I/F 320 (e.g., for connecting to a computer system; dock;charging station; input devices, such as a microphone, camera, keyboard;output devices, such as speakers; etc.), the display 360, which may beintegrated with or external to the communication device 106, andcellular communication circuitry 330 such as for 5G NR, LTE, GSM, etc.,and short to medium range wireless communication circuitry 329 (e.g.,Bluetooth™ and WLAN circuitry). In some embodiments, communicationdevice 106 may include wired communication circuitry (not shown), suchas a network interface card, e.g., for Ethernet.

The cellular communication circuitry 330 may couple (e.g.,communicatively; directly or indirectly) to one or more antennas, suchas antennas 335 and 336 as shown. The short to medium range wirelesscommunication circuitry 329 may also couple (e.g., communicatively;directly or indirectly) to one or more antennas, such as antennas 337and 338 as shown. Alternatively, the short to medium range wirelesscommunication circuitry 329 may couple (e.g., communicatively; directlyor indirectly) to the antennas 335 and 336 in addition to, or insteadof, coupling (e.g., communicatively; directly or indirectly) to theantennas 337 and 338. The short to medium range wireless communicationcircuitry 329 and/or cellular communication circuitry 330 may includemultiple receive chains and/or multiple transmit chains for receivingand/or transmitting multiple spatial streams, such as in amultiple-input multiple output (MIMO) configuration.

In some embodiments, as further described below, cellular communicationcircuitry 330 may include dedicated receive chains (including and/orcoupled to, e.g., communicatively; directly or indirectly. dedicatedprocessors and/or radios) for multiple RATs (e.g., a first receive chainfor LTE and a second receive chain for 5G NR). In addition, in someembodiments, cellular communication circuitry 330 may include a singletransmit chain that may be switched between radios dedicated to specificRATs. For example, a first radio may be dedicated to a first RAT, e.g.,LTE, and may be in communication with a dedicated receive chain and atransmit chain shared with an additional radio, e.g., a second radiothat may be dedicated to a second RAT, e.g., 5G NR, and may be incommunication with a dedicated receive chain and the shared transmitchain.

The communication device 106 may also include and/or be configured foruse with one or more user interface elements. The user interfaceelements may include any of various elements, such as display 360 (whichmay be a touchscreen display), a keyboard (which may be a discretekeyboard or may be implemented as part of a touchscreen display), amouse, a microphone and/or speakers, one or more cameras, one or morebuttons, and/or any of various other elements capable of providinginformation to a user and/or receiving or interpreting user input.

The communication device 106 may further include one or more smart cards345 that include SIM (Subscriber Identity Module) functionality, such asone or more UICC(s) (Universal Integrated Circuit Card(s)) cards 345.

As shown, the SOC 300 may include processor(s) 302, which may executeprogram instructions for the communication device 106 and displaycircuitry 304, which may perform graphics processing and provide displaysignals to the display 360. The processor(s) 302 may also be coupled tomemory management unit (MMU) 340, which may be configured to receiveaddresses from the processor(s) 302 and translate those addresses tolocations in memory (e.g., memory 306, read only memory (ROM) 350, NANDflash memory 310) and/or to other circuits or devices, such as thedisplay circuitry 304, short range wireless communication circuitry 229,cellular communication circuitry 330, connector I/F 320, and/or display360. The MMU 340 may be configured to perform memory protection and pagetable translation or set up. In some embodiments, the MMU 340 may beincluded as a portion of the processor(s) 302.

As noted above, the communication device 106 may be configured tocommunicate using wireless and/or wired communication circuitry. Thecommunication device 106 may be configured to transmit a request toattach to a first network node operating according to the first RAT andtransmit an indication that the wireless device is capable ofmaintaining substantially concurrent connections with the first networknode and a second network node that operates according to the secondRAT. The wireless device may also be configured transmit a request toattach to the second network node. The request may include an indicationthat the wireless device is capable of maintaining substantiallyconcurrent connections with the first and second network nodes. Further,the wireless device may be configured to receive an indication that dualconnectivity (DC) with the first and second network nodes has beenestablished.

As described herein, the communication device 106 may include hardwareand software components for implementing features for using RRCmultiplexing to perform transmissions according to multiple radio accesstechnologies in the same frequency carrier, as well as the various othertechniques described herein. The processor 302 of the communicationdevice 106 may be configured to implement part or all of the featuresdescribed herein, e.g., by executing program instructions stored on amemory medium (e.g., a non-transitory computer-readable memory medium).Alternatively (or in addition), processor 302 may be configured as aprogrammable hardware element, such as an FPGA (Field Programmable GateArray), or as an ASIC (Application Specific Integrated Circuit).Alternatively (or in addition) the processor 302 of the communicationdevice 106, in conjunction with one or more of the other components 300,304, 306, 310, 320, 329, 330, 340, 345, 350, 360 may be configured toimplement part or all of the features described herein.

In addition, as described herein, processor 302 may include one or moreprocessing elements. Thus, processor 302 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof processor 302. In addition, each integrated circuit may includecircuitry (e.g., first circuitry, second circuitry, etc.) configured toperform the functions of processor(s) 302.

Further, as described herein, cellular communication circuitry 330 andshort range wireless communication circuitry 329 may each include one ormore processing elements. In other words, one or more processingelements may be included in cellular communication circuitry 330 and,similarly, one or more processing elements may be included in shortrange wireless communication circuitry 329. Thus, cellular communicationcircuitry 330 may include one or more integrated circuits (ICs) that areconfigured to perform the functions of cellular communication circuitry330. In addition, each integrated circuit may include circuitry (e.g.,first circuitry, second circuitry, etc.) configured to perform thefunctions of cellular communication circuitry 230. Similarly, the shortrange wireless communication circuitry 329 may include one or more ICsthat are configured to perform the functions of short range wirelesscommunication circuitry 32. In addition, each integrated circuit mayinclude circuitry (e.g., first circuitry, second circuitry, etc.)configured to perform the functions of short range wirelesscommunication circuitry 329.

FIG. 4 —Block Diagram of a Base Station

FIG. 4 illustrates an example block diagram of a base station 102,according to some embodiments. It is noted that the base station of FIG.4 is merely one example of a possible base station. As shown, the basestation 102 may include processor(s) 404 which may execute programinstructions for the base station 102. The processor(s) 404 may also becoupled to memory management unit (MMU) 440, which may be configured toreceive addresses from the processor(s) 404 and translate thoseaddresses to locations in memory (e.g., memory 460 and read only memory(ROM) 450) or to other circuits or devices.

The base station 102 may include at least one network port 470. Thenetwork port 470 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 106, access to thetelephone network as described above in FIGS. 1 and 2 .

The network port 470 (or an additional network port) may also oralternatively be configured to couple to a cellular network, e.g., acore network of a cellular service provider. The core network mayprovide mobility related services and/or other services to a pluralityof devices, such as UE devices 106. In some cases, the network port 470may couple to a telephone network via the core network, and/or the corenetwork may provide a telephone network (e.g., among other UE devicesserviced by the cellular service provider).

In some embodiments, base station 102 may be a next generation basestation, e.g., a 5G New Radio (5G NR) base station, or “gNB”. In suchembodiments, base station 102 may be connected to a legacy evolvedpacket core (EPC) network and/or to a NR core (NRC) network. Inaddition, base station 102 may be considered a 5G NR cell and mayinclude one or more transition and reception points (TRPs). In addition,a UE capable of operating according to 5G NR may be connected to one ormore TRPs within one or more gNBs.

The base station 102 may include at least one antenna 434, and possiblymultiple antennas. The at least one antenna 434 may be configured tooperate as a wireless transceiver and may be further configured tocommunicate with UE devices 106 via radio 430. The antenna 434communicates with the radio 430 via communication chain 432.Communication chain 432 may be a receive chain, a transmit chain orboth. The radio 430 may be configured to communicate via variouswireless communication standards, including, but not limited to, 5G NR,LTE, LTE-A, GSM, UMTS, CDMA2000, Wi-Fi, etc.

The base station 102 may be configured to communicate wirelessly usingmultiple wireless communication standards. In some instances, the basestation 102 may include multiple radios, which may enable the basestation 102 to communicate according to multiple wireless communicationtechnologies. For example, as one possibility, the base station 102 mayinclude an LTE radio for performing communication according to LTE aswell as a 5G NR radio for performing communication according to 5G NR.In such a case, the base station 102 may be capable of operating as bothan LTE base station and a 5G NR base station. As another possibility,the base station 102 may include a multi-mode radio which is capable ofperforming communications according to any of multiple wirelesscommunication technologies (e.g., 5G NR and Wi-Fi, LTE and Wi-Fi, LTEand UMTS, LTE and CDMA2000, UMTS and GSM, etc.).

As described further subsequently herein, the BS 102 may includehardware and software components for implementing or supportingimplementation of features described herein. The processor 404 of thebase station 102 may be configured to implement or supportimplementation of part or all of the methods described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively, theprocessor 404 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit), or a combination thereof. Alternatively(or in addition) the processor 404 of the BS 102, in conjunction withone or more of the other components 430, 432, 434, 440, 450, 460, 470may be configured to implement or support implementation of part or allof the features described herein.

In addition, as described herein, processor(s) 404 may include one ormore processing elements. Thus, processor(s) 404 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof processor(s) 404. In addition, each integrated circuit may includecircuitry (e.g., first circuitry, second circuitry, etc.) configured toperform the functions of processor(s) 404.

Further, as described herein, radio 430 may include one or moreprocessing elements. Thus, radio 430 may include one or more integratedcircuits (ICs) that are configured to perform the functions of radio430. In addition, each integrated circuit may include circuitry (e.g.,first circuitry, second circuitry, etc.) configured to perform thefunctions of radio 430.

FIG. 5 —Block Diagram of Cellular Communication Circuitry

FIG. 5 illustrates an example simplified block diagram of cellularcommunication circuitry, according to some embodiments. It is noted thatthe block diagram of the cellular communication circuitry of FIG. 5 isonly one example of a possible cellular communication circuit; othercircuits, such as circuits including or coupled to sufficient antennasfor different RATs to perform uplink activities using separate antennas,are also possible. According to embodiments, cellular communicationcircuitry 330 may be included in a communication device, such ascommunication device 106 described above. As noted above, communicationdevice 106 may be a user equipment (UE) device, a mobile device ormobile station, a wireless device or wireless station, a desktopcomputer or computing device, a mobile computing device (e.g., a laptop,notebook, or portable computing device), a tablet and/or a combinationof devices, among other devices.

The cellular communication circuitry 330 may couple (e.g.,communicatively; directly or indirectly) to one or more antennas, suchas antennas 335 a-b and 336 as shown (in FIG. 3 ). In some embodiments,cellular communication circuitry 330 may include dedicated receivechains (including and/or coupled to, e.g., communicatively; directly orindirectly. dedicated processors and/or radios) for multiple RATs (e.g.,a first receive chain for LTE and a second receive chain for 5G NR). Forexample, as shown in FIG. 5 , cellular communication circuitry 330 mayinclude a modem 510 and a modem 520. Modem 510 may be configured forcommunications according to a first RAT, e.g., such as LTE or LTE-A, andmodem 520 may be configured for communications according to a secondRAT, e.g., such as 5G NR.

As shown, modem 510 may include one or more processors 512 and a memory516 in communication with processors 512. Modem 510 may be incommunication with a radio frequency (RF) front end 530. RF front end530 may include circuitry for transmitting and receiving radio signals.For example, RF front end 530 may include receive circuitry (RX) 532 andtransmit circuitry (TX) 534. In some embodiments, receive circuitry 532may be in communication with downlink (DL) front end 550, which mayinclude circuitry for receiving radio signals via antenna 335 a.

Similarly, modem 520 may include one or more processors 522 and a memory526 in communication with processors 522. Modem 520 may be incommunication with an RF front end 540. RF front end 540 may includecircuitry for transmitting and receiving radio signals. For example, RFfront end 540 may include receive circuitry 542 and transmit circuitry544. In some embodiments, receive circuitry 542 may be in communicationwith DL front end 560, which may include circuitry for receiving radiosignals via antenna 335 b.

In some embodiments, a switch 570 may couple transmit circuitry 534 touplink (UL) front end 572. In addition, switch 570 may couple transmitcircuitry 544 to UL front end 572. UL front end 572 may includecircuitry for transmitting radio signals via antenna 336. Thus, whencellular communication circuitry 330 receives instructions to transmitaccording to the first RAT (e.g., as supported via modem 510), switch570 may be switched to a first state that allows modem 510 to transmitsignals according to the first RAT (e.g., via a transmit chain thatincludes transmit circuitry 534 and UL front end 572). Similarly, whencellular communication circuitry 330 receives instructions to transmitaccording to the second RAT (e.g., as supported via modem 520), switch570 may be switched to a second state that allows modem 520 to transmitsignals according to the second RAT (e.g., via a transmit chain thatincludes transmit circuitry 544 and UL front end 572).

In some embodiments, the cellular communication circuitry 330 may beconfigured to transmit, via the first modem while the switch is in thefirst state, a request to attach to a first network node operatingaccording to the first RAT and transmit, via the first modem while theswitch is in a first state, an indication that the wireless device iscapable of maintaining substantially concurrent connections with thefirst network node and a second network node that operates according tothe second RAT. The wireless device may also be configured transmit, viathe second radio while the switch is in a second state, a request toattach to the second network node. The request may include an indicationthat the wireless device is capable of maintaining substantiallyconcurrent connections with the first and second network nodes. Further,the wireless device may be configured to receive, via the first radio,an indication that dual connectivity with the first and second networknodes has been established.

As described herein, the modem 510 may include hardware and softwarecomponents for implementing features for using RRC multiplexing toperform transmissions according to multiple radio access technologies inthe same frequency carrier, as well as the various other techniquesdescribed herein. The processors 512 may be configured to implement partor all of the features described herein, e.g., by executing programinstructions stored on a memory medium (e.g., a non-transitorycomputer-readable memory medium). Alternatively (or in addition),processor 512 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit). Alternatively (or in addition) theprocessor 512, in conjunction with one or more of the other components530, 532, 534, 550, 570, 572, 335 and 336 may be configured to implementpart or all of the features described herein.

In addition, as described herein, processors 512 may include one or moreprocessing elements. Thus, processors 512 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof processors 512. In addition, each integrated circuit may includecircuitry (e.g., first circuitry, second circuitry, etc.) configured toperform the functions of processors 512.

As described herein, the modem 520 may include hardware and softwarecomponents for implementing features for using RRC multiplexing toperform transmissions according to multiple radio access technologies inthe same frequency carrier, as well as the various other techniquesdescribed herein. The processors 522 may be configured to implement partor all of the features described herein, e.g., by executing programinstructions stored on a memory medium (e.g., a non-transitorycomputer-readable memory medium). Alternatively (or in addition),processor 522 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit). Alternatively (or in addition) theprocessor 522, in conjunction with one or more of the other components540, 542, 544, 550, 570, 572, 335 and 336 may be configured to implementpart or all of the features described herein.

In addition, as described herein, processors 522 may include one or moreprocessing elements. Thus, processors 522 may include one or moreintegrated circuits (ICs) that are configured to perform the functionsof processors 522. In addition, each integrated circuit may includecircuitry (e.g., first circuitry, second circuitry, etc.) configured toperform the functions of processors 522.

FIGS. 6-7 —5G NR Architecture

In some implementations, fifth generation (5G) wireless communicationwill initially be deployed concurrently with other wirelesscommunication standards (e.g., LTE). For example, whereas FIG. 6illustrates a possible standalone (SA) implementation of a nextgeneration core (NGC) network 606 and 5G NR base station (e.g., gNB604), dual connectivity between LTE and 5G new radio (5G NR or NR), suchas in accordance with the exemplary non-standalone (NSA) architectureillustrated in FIG. 7 , has been specified as part of the initialdeployment of NR. Thus, as illustrated in FIG. 7 , evolved packet core(EPC) network 600 may continue to communicate with current LTE basestations (e.g., eNB 602). In addition, eNB 602 may be in communicationwith a 5G NR base station (e.g., gNB 604) and may pass data between theEPC network 600 and gNB 604. In some instances, the gNB 604 may alsohave at least a user plane reference point with EPC network 600. Thus,EPC network 600 may be used (or reused) and gNB 604 may serve as extracapacity for UEs, e.g., for providing increased downlink throughput toUEs. In other words, LTE may be used for control plane signaling and NRmay be used for user plane signaling. Thus, LTE may be used to establishconnections to the network and NR may be used for data services. As willbe appreciated, numerous other non-standalone architecture variants arepossible.

FIG. 8 —CSI Encoding with Reduced Overhead

As noted above, a UE 106 and BS 102 may each include any number ofantennas/ports and may be configured to use the antennas to transmitand/or receive directional wireless signals (e.g., beams). To receiveand/or transmit such directional signals, the antennas of the UE 106and/or BS 102 may be configured to apply different “weights” todifferent antennas. The process of applying these different weights maybe referred to as “precoding”.

Channel state information (CSI) may refer to the properties of awireless channel, e.g., between a UE 106 and BS 102. CSI may beestimated (e.g., in the downlink direction) by the UE 106 and reportedback to the BS 102. CSI may be reported, at least in part via aprecoding matrix indicator (PMI). The BS 102 may then use the CSI (e.g.,potentially multiple PMIs) for precoding.

NR release 15 includes Type I and Type II CSI. Type II CSI may includeboth wideband (WB) and subband (SB)-specific information, e.g., for eachlayer and for each polarization. Amplitude coefficients may be reportedfor both WB and SB. With Type II CSI, the (e.g., SB-specific) precodingweights for a layer may be represented by a linear combination of a setof discrete Fourier transform (DFT) vectors (e.g., beams). The vectorsmay be 2-dimensional fast Fourier transform (FFT) based. In addition toamplitude coefficients, SB-specific phase coefficients may be reportedfor each beam, layer, and polarization. The linear combinationcoefficients in a Type II CSI may be element-wise quantized for each SBand for each polarization. Thus, Type II CSI may require large amountsof signaling overhead, e.g., to enumerate a potentially large number ofSB-specific combination coefficients in the precoding vector.

A Type II precoder using linear combination of beams has been proposedfor adoption in 3GPP standards for MU-MIMO. The UE feedback for theprecoder may involve a linear combination of beams and may include bothWB and SB amplitude coefficients as well as phase information. Currently3GPP standards may support rank 1 and rank 2. The Type II CSI's largepayload may demand high payload overhead, e.g., including sufficientresources from a gNB.

For each layer, the precoding vector may be a linear combination of anumber (L) of DFT vectors, e.g., beams. A wireless device (e.g., UE) mayselect a 2D beam basis set for a CSI report along horizontal andvertical polarizations. The length of each DFT vector/beam maycorrespond to the size of the array of antennas (e.g., an array of N₁ byN₂ antennas may imply DFT vectors of length N₁N₂ (e.g., N₁*N₂)). The DFTvectors may be common for all SBs. For example, the (L) DFT vectors maybe block diagonal matrix which may be multiplied by a column ofSB-specific combination coefficients.

WB PMI may encode various information, including rotation in eachspatial dimension, indices of the (L) spatial basis, a strongestcoefficient for each layer, and a WB amplitude for each layer. SB PMImay include SB phase and (e.g., if configured) SB amplitude. The numberof non-zero coefficients may determine the number of bits of PMI foreach SB.

Frequency compression may be applied to reduce overhead. For example, ifthe channel is less frequency-selective, neighboring coefficients mayexhibit similarity (e.g., SB-specific coefficients may be correlated).Therefore, overhead may be reduced by compression in the frequencydimension, e.g., by compressing coefficients of a number (N) of SBs to asmaller number (K) of frequency basis (which may also be referred to as“taps”). This may be referred to as a K DFT basis.

An aggregation of precoding vectors may be expressed as a matrix. Thematrix may be equal to a product of a matrix of the L DFT vectors (e.g.,the spatial basis or “beams”) multiplied by a block diagonal matrix ofthe compressed combination coefficients multiplied by the K frequencybasis.

Notwithstanding the above techniques, the size of a (e.g., Type II) CSIreport may be quite large. For example, due to the number ofantennas/beams and SB s, the number of SB-specific coefficients may belarge (e.g., even after frequency compression). Accordingly, furthertechniques for reducing CSI overhead may be desired.

Some embodiments may reduce this payload and resource need. While a UEmay send a full CSI report (e.g., a full precoder) to the gnB (or BS102), it may also send a partial CSI report containing the data requiredfor precoder construction at the gnB. The gnB may do some additionalprocessing to reconstruct the precoder. Thus, the following approachesand embodiments may present a tradeoff between additional processing andoverhead reduction. Briefly, embodiments may include any or all of: beamsplitting across time domain, layer wise puncturing with reconstructionat the gnB, and/or randomized SB compression with simple convexoptimization the gnB. In some embodiments, overhead reduction schemesmay be traded off with increase in complexity at the gnB.

FIG. 8 illustrates exemplary techniques for reducing overhead in CSIencoding, e.g., particularly for higher numbers of layers relative totechniques employed in NR release 15. Embodiments described herein mayinclude reducing overhead via any combination of beam splitting, layerpuncturing across orthogonal layers, and/or random SB compression.Aspects of the method of FIG. 8 may be implemented by a wireless device,such as the UEs 106, in communication with one or more base station(e.g., BS 102) as illustrated in and described with respect to theFigures, or more generally in conjunction with any of the computersystems or devices shown in the Figures, among other devices, asdesired. Note that while at least some elements of the method aredescribed in a manner relating to the use of communication techniquesand/or features associated with 3GPP specification documents, suchdescription is not intended to be limiting to the disclosure, andaspects of the method may be used in any suitable wireless communicationsystem, as desired. Similarly, although some elements of the method aredescribed in a manner relating to the measurement and reporting of adownlink channel (e.g., by a UE reporting to a base station), the methodmay also be applied in the reverse (e.g., a base station measuring anuplink channel). Further, the method may be applied in other contexts(e.g., between multiple UEs, e.g., in device-to-device communications).In various embodiments, some of the elements of the methods shown may beperformed concurrently, in a different order than shown, may besubstituted for by other method elements, or may be omitted. Additionalmethod elements may also be performed as desired. As shown, the methodmay operate as follows.

A wireless device (e.g., UE 106) may establish communication with a basestation (e.g., BS 102) (802), according to some embodiments. The UE 106and BS 102 may communicate according to one or more wireless standards(e.g., NR, among various possibilities) and may exchange applicationdata and/or control information in the uplink and/or downlinkdirections. The connection between the UE 106 and BS 102 may usemultiple-in-multiple out (MIMO), including multi-user MIMO (MU-MIMO).The communication may use any number of bands and/or SBs, e.g.,including licensed and/or unlicensed frequencies. The communication mayuse any number of antennas/ports at the UE 106 and/or BS 102. The UE 106and/or BS 102 may use beamforming techniques and may weight the variousantennas differently, e.g., to transmit and/or receive any number ofbeams, e.g., in various directions.

The BS 102 may provide control information to the UE, according to someembodiments. The control information may specify configurationparameters for measuring and reporting channel state information (CSI).For example, the configuration parameters may include timing ofmeasurements and/or reports, frequencies (e.g., bands and/or SBs) tomeasure and/or report, beams to measure and/or report, techniques toapply for reporting CSI (e.g., potentially including one or more of:beam splitting, layer puncturing across orthogonal layers, random SBcompression, and/or full reporting, among various possibilities), etc.The control information may indicate that the UE should report spatialbasis amplitude, frequency basis amplitude, or both. The controlinformation may be transmitted to the UE via a higher layer such asradio resource control (RRC) and/or media access control (MAC), amongvarious possibilities.

The wireless device (e.g., UE 106) may perform one or more measurementsto measure the state of the channel, e.g., according to received controlinformation and/or configuration of the UE (804), according to someembodiments. The measurements may include any radio link measurements,e.g., to support reports such as CSI and/or channel quality indicator(CQI). For example, the measurements may include one or more of:signal-noise ratio (SNR), signal to interference and noise ratio (SINR),reference signal received power (RSRP), reference signal receivedquality (RSRQ), received signal strength indicator (RSSI), block errorrate (BLER), bit error rate (BER), channel impulse response (CIR),channel error response (CER), etc. The measurements may be performedusing any number of receive beams (e.g., of the UE 106) and/or transmitbeams (e.g., of the BS 102). The measurements may be performed for anynumber of frequencies (e.g., SB and/or WB measurements). Themeasurements may be performed using reference signals (RS) (e.g.,CSI-RS) transmitted by the BS 102. The measurements may be performed atany time(s), and may utilize hysteresis techniques.

Based on the channel state measurements and any control information,wireless device (e.g., UE 106) may encode CSI, e.g., including the PMIand/or other information (806), according to some embodiments. The CSImay be encoded into one or more CSI reports or incorporated into anotherreport/transmission. Each CSI report may include any number of parts,e.g., fields or bits.

To encode the CSI, the wireless device (e.g., UE 106) may dynamicallyselect one or more technique or method to reduce the overhead associatedwith transmitting the CSI. Such techniques may include any or all ofbeam splitting (e.g., across time domain) (808), layer puncturing acrossorthogonal layers (e.g., layer wise puncturing with reconstruction atgnB) (810), and/or randomized SB compression (e.g., with simple convexoptimization gnB) (812), among various possibilities. The UE maydetermine which (if any) techniques to apply based on one or more of: anindication from the BS (e.g., in control information), configuration ofthe UE, channel conditions, rank (e.g., current number of layers inuse), report size (e.g., of potential reports using the differenttechniques), motion of the UE (e.g., which may lead to changing channelconditions), activity of the user and/or applications executing on thedevice (e.g., small report size may be prioritized if activity is low,more detailed/accurate reporting may be prioritized if activity and/orperformance requirements are high), etc. For example, at various timesand/or under various circumstances, a UE may select differentcombinations of techniques, e.g., including to transmit full CSI reportswithout applying any of beam splitting, layer puncturing, or SBcompression. For example, at a first time (e.g., at a firstfrequency/periodicity) a UE may transmit one or more CSI reports using atechnique for reducing overhead, and at a second time (e.g., at a lowerfrequency or longer periodicity) the UE may transmit a report with fullPMI.

Beam splitting, as explained in more detail below with regard to FIGS.17-18 , may include dividing CSI into any number of reports, e.g., whichmay be transmitted at different times. The various reports may includecomplementary portions of the CSI, e.g., a first report may include afirst subset of coefficients and a second report may include a second,complementary, subset of coefficients. For example, a first report mayinclude information about all layers at a lower level of detail and asecond report may include information about a single layer at a higherlevel of detail. As a second example a first report may include a firstsubset of beams and a second report may include a second subset ofbeams. In some embodiments, more than two reports may be used. Beamsplitting may not rely on additional processing at the BS to the samedegree as the other techniques (e.g., layer puncturing, randomized SBcompression), but may offer comparatively lower benefits in terms ofoverhead reduction, according to some embodiments.

Layer puncturing across orthogonal layers, as explained in more detailbelow with regard to FIGS. 19-22 , may include omitting coefficients fora number of beams from a CSI report (e.g., for all SBs). The receivermay determine the values of the omitted coefficients using mathematicalproperties of the precoder, e.g., orthogonality. Coefficients forincreasing numbers of beams may be omitted for each layer.

Randomized SB compression as explained in more detail below with regardto FIG. 23 , may include selecting a random subset of SBs for reporting.The size of the random subset of SBs may be based on time domain supportas indicated by channel impulse response (CIR) and/or channel energyresponse (CER), among various possibilities. The receiver may determinethe coefficients (e.g., for SBs that are excluded) using convexoptimization techniques.

Any combination of the illustrated techniques may be applied together(e.g., in any order). For example, layer puncturing may be applied toomit coefficients of some beams (e.g., across all SBs) from the report.Then, SB compression may be further applied to omit coefficients (e.g.,for all beams) for some SBs from the report.

The wireless device (e.g., UE 106) may transmit the CSI to the BS 102(814), according to some embodiments. The CSI may be transmitted on ashared and/or control channel. The CSI report(s) may be periodic oraperiodic. The report(s) may be transmitted alone or with additionalcontrol information, measurement reports, and/or application data.

The BS 102 may receive and decode the CSI report(s). The BS mayinterpret the CSI reports in view of the applied technique(s) forreducing overhead. In other words, the BS may reconstruct any omittedcoefficients according to the mathematical techniques described herein.

The wireless device (e.g., UE 106) may exchange data with the BS 102(816), according to some embodiments. One or both of the UE 106 and BS102 may use precoding to exchange data, e.g., according to the CSI,among various possibilities. The exchange of data may include controlinformation and/or application data. The control information may specifyuse (e.g., by the UE 106 and/or BS 102) of precoding according to theCSI report. Control information specifying configurations for future CSIreports may be included. Such future CSI reports may use the same ordifferent techniques for encoding CSI.

FIG. 9 —Antenna Array Layout

FIG. 9 illustrates the layout of an exemplary array of antennas,according to some embodiments. N₁ and N₂ may refer to the number ofantennas in each of two respective dimensions. As shown, the exemplaryarray is a two-dimensional array consisting of a 4 by 2 grid (e.g.,N₁=4, N₂=2). Thus, the exemplary array includes 8 antennas (e.g.,N₁*N₂=8). The number of DFT vectors may be configured (e.g., by a BS)based on the values of N₁ and N₂ or separately from the values of N₁ andN₂. In some embodiments, the total number of antennas may range from 4to 8, although other numbers of antennas are possible according tovarious embodiments. Further, the array may include different numbers ofdimensions (e.g., one or 3 dimensions, etc.). Similarly, the antennasmay be arranged in other patterns (e.g., concentric circles, etc.). Anantenna array (e.g., of N₁ and N₂) may be able to receive, transmit, andor report on a number of beams, L, e.g., as a linear combination.

FIG. 10 —Table of Ports, Antenna Layouts, and Oversampling Rates

FIG. 10 illustrates various possible combinations of number of ports(e.g., for CSI-RS, e.g., a number of antennas), antenna layouts, andoversampling rates, according to some embodiments. Such combinations maybe useful for Type II CSI feedback, e.g., high-resolution CSI such asMU-MIMO and rank greater than or equal to 2, e.g., for millimeter wave(mmWave) communications. The FFT oversampling rate may be expressed intwo dimensions corresponding to N₁ and N₂, e.g., (O₁, O₂).

FIGS. 11 and 12 —Type II CSI Precoding

FIG. 11 illustrates a precoder for type II CSI, e.g., utilizing soundingreference signal (SRS) based channel estimation for reduced beamfeedback. It will be appreciated that various types of RS may be used,e.g., SRS, CSI-RS, etc. An antenna array may be able to receive,transmit, and or report on a number of beams, L, e.g., as a linearcombination of beams b₀ to b₃ in the illustrated example. The phasecombinations may be represented by phase shift keying (e.g., nPSK). Fortype II CSI reporting, SB amplitude may be either on or off, e.g., mayor may not be reported in CSI. Rank (e.g., number of layers) may beindicated by rank indicator (RI).

As shown, a first matrix (1101) representing beams b₀ to b₃ across thehorizontal (H) and vertical (V) polarizations may be multiplied by asecond matrix (1102). The second matrix may include coefficients (c_(m)^(r)) for each layer (r), SB, and beam (indexed by m, illustrated in thevertical dimension so that m=0-3 or a first polarization and m=4-7 forthe second polarization). The third matrix (1103) illustrates thesummation of the coefficients multiplied by the beams, e.g., the productof the first two matrices.

FIG. 12 further illustrates precoding for type II CSI. A basic conceptof Type II CSI feedback may be the linear combination of beams (e.g.,DFT beams). For each layer, up to 4 component beams (e.g., 2D FFT based)may be selected and the amplitude coefficients (e.g., WB and SB) and thephase coefficient (SB) for each selected beam, each layer and eachpolarization may be reported.

In some embodiments, the UE may report all coefficients c_(m) ^(r) forall beams, layers, and SBs. The coefficients may be further reported asWB amplitude (p⁽¹⁾), SB amplitude (p⁽²⁾), and SB phase φ.

FIGS. 13-16 Type II CSI Reporting

FIG. 13 illustrates Type II CSI reporting with rank 1, according to someembodiments. A UE may select a 2D beam basis set for CSI reporting alonghorizontal and vertical polarizations. The UE may report different beamcoefficients, WB and/or SB amplitudes, and/or phase coefficients (SB)for each selected beam per each layer and polarization. The table (1301)shows the number of bits (except for the first two columns, whichillustrate rank and number of beams per layer, respectively) that may beused to indicate the precoding parameter of the column. Arrows indicatehow the bits correspond to the mathematical representation of theprecoder (e.g., similar to the illustration of FIG. 12 ).

As illustrated in the first row of the table 1301, the total WB payloadmay be 23 bits, in the illustrated example. This 23 bits may be the sumof the bits for rotation (4), beam selection (8), strongest coefficient(2), and WB amplitude (9). The total payload in this row may be the sumof the WB payload (23) and the SB payload per SB times the number ofSBs. In the illustrated example, the payload per SB is SB amplitude (3)plus SB phase (9), and there are 10 SBs. Thus, there are 12 bits foreach of 10 SBs, for 120 bits for SB payload and 143 bits of totalpayload.

In some embodiments, the type II CSI reports may contain same L beamsfor horizontal and vertical polarizations selected from a set of N₁*N₂orthogonal beams. Further over sampling by O₁ and O₂ may increase theresolution of the beams. So the 2L (L vertical and L horizontal beams)may be weighted by 2L wideband amplitudes (p_(ii) in FIG. 13 ) cascadedwith SB amplitude and phase coefficients. The beam with the highestamplitude coefficient may be weighted by factor of 1 implicitly and restof (2L−1) beams may be weighted by 3 bits for Wideband and 1 bit for SBamplitude for L−1 beams. 2 bit Phase coefficients may be allocated for2L beams per SB.

FIG. 14 illustrates type II CSI reporting with rank 1 and 2, accordingto some embodiments. When the number of layers is increased to 2, thewhole configuration (e.g., of FIG. 13 ) may be repeated for anotherlayer. For example, the same beams may be chosen for the second layer aswell. A UE may select the same beam basis set for all layers per CSIreport along horizontal and vertical polarizations. The UE may reportdifferent beam coefficients, WB amplitudes, SB amplitudes, and phasecoefficients (SB) for each selected beam per each layer andpolarization. Accordingly, each layer may add a column to the precoder,as illustrated. Note that the bit size of most columns in the table maydouble from rank 1 to rank 2 (for a given number of layers). However,some fields (e.g., rotation and beam selection) may not be changed bythe rank. Thus, the SB payload may scale with rank and some of thefields of the WB payload may scale with rank. In other words, the SBfeedback may double owing to the (e.g., doubled) number of layers. Thisapproach may extend to higher ranks as shown in FIG. 15 , and theoverhead required for rank 3 and rank 4 transmissions may be as shown.

FIG. 15 illustrates type II CSI reporting with rank 1-4, according tosome embodiments. FIG. 15 illustrates the bit size that would be neededto extend the techniques of FIGS. 13 and 14 to ranks 3 and 4 using thesame values of L, e.g., L={2, 3, 4} beams.

FIG. 16 illustrates type II CSI reporting over time, according to someembodiments. As illustrated, at a first time (t0) a base station (gNB)may transmit a CSI request. At a second time, the UE may respond bytransmitting a first CSI report. In the illustrated example, the firstreport may be based on rank 3 with L=4 beams. At a third time (t0+y),the base station (gNB) may transmit a second CSI request. At a fourthtime, the UE may respond by transmitting a second CSI report. In theillustrated example, the second report may be based on rank 3 with L=4beams. It should be noted that, although the parameters of the first andsecond report are the same in the illustrated example, the parameters(e.g., rank, number of beams, etc.) may vary between reports. Each ofthe reports may be 812 bits, among various possibilities.

FIGS. 17-18 Type II CSI Precoding Overhead Reduction Via Beam Splitting

FIG. 17 illustrates type II CSI precoding overhead reduction via beamsplitting, according to some embodiments. Type II CSI overhead may bereduced by dividing CSI report information among multiple (e.g., 2 or 3,among various possibilities) CSI reports. For example, a CSI report forn layers and x beams may be split into two (e.g., complementary,partial) CSI reports: a first report (e.g., CSI1 or PMI1) with n layersand k beams and a second report (e.g., CSI2 or PMI2) with 1 layer andx-k beams. The k strongest beams may be selected for the first report;the weaker beams may be included in the second report. The second reportmay be constructed based on a rank 1 layer, e.g., including a singlevalue for each parameter for each beam rather than includinglayer-specific values for each parameter for each beam. In other words,the first CSI report may contain feedback on rank r layers and k beamswhile the second report may be limited to a rank 1 layer. For both CSIreports the UE may report the same rank (e.g., as shown, the UE mayreport the rank in both reports, even though the second report may onlyinclude values for a single layer) and based on the same channel.

In some embodiments, CQI may be made pessimistic on the first report andoptimistic/realistic on the second report. In other words, when the BSdoes not have the full beam information (e.g., the first report providesonly partial PMI information), a UE may report (e.g., slightly) lowerCQI to keep the potentially higher bit error rate (BER) and/or blockerror rate (BLER) in check due to the lack of full beam information atBS. For example, a BS may control the BER/BLER by adjusting themodulation and coding scheme (MCS) scheduled. Thus, by reporting a lowerCQI, the UE may cause the BS to schedule a more conservative MCS, thusmitigating a potentially negative impact on BER/BLER due to theincomplete PMI information in the first report. Subsequently once thefull beam info is acquired by the BS (e.g., via the second report), UEcan report the actual CQI.

Performance loss on the first report may be compensated by a betterresolution beam on the second report. For example, in the case that k=1,the first report may provide relatively low spatial resolution (e.g.,only including coefficients for a single, strongest beam). The secondreport may compensate by providing a higher spatial resolution (e.g.,more beams). In other words, the BS may use the spatial resolution ofthe second report to compensate for the low spatial resolution of thefirst report, e.g., to approximate at least one coefficient omitted fromthe first report.

FIG. 18 illustrates type II CSI precoding overhead reduction via beamsplitting over time, according to some embodiments. FIG. 18 may becompared to FIG. 16 , e.g., the rank may be 3 and L may=4 beams.However, in the example of FIG. 18 , the UE may apply beam splitting toreduce CSI overhead. As illustrated in FIG. 18 , at a first time (t0) abase station (gNB) may transmit a CSI request. In some embodiments, therequest may indicate that the UE should reduce overhead in reportingCSI, e.g., via beam splitting.

At a second time (t0+z), the UE may respond by transmitting a first(e.g., partial) CSI report using beam splitting (k=1). In theillustrated example, the first report may be based on rank 3 with L=3beams (e.g., the strongest beam is represented for each of 3 layers for3 total beams). Note that the coefficients are summed only over 3 layersrather than 4 (e.g., as in FIG. 17 ). The first report may be 550 bits,among various possibilities.

At a third time (t0+2z), the UE may transmit a second (e.g., partial)CSI report. The second partial report may complement the first partialCSI report, e.g., as described above with respect to FIG. 17 . Thus, theUE may provide coefficients for only a single (e.g., rank 1) layer inthe second report. However, it should be noted that the UE may stillreport rank 3 in the second report. The second report may also includevalues for L=3 beams, for that layer. Thus, as shown, the second reportmay include only the single layer (note that no summations are shown).The second report may be 194 bits, among various possibilities.

It should be noted that, although the illustrated example shows thetransmission of the first and second reports at different times, thisspacing in time is not required. The reports may be transmittedsequentially, concurrently, in reverse order, or with any desiredspacing in time.

At a fourth time (t0+y) the base station (gNB) may transmit a second CSIrequest. At a later time (not shown), the UE may respond by transmittingone or more additional CSI reports. The additional report(s) may or maynot reduce overhead via beam splitting (e.g., according to anindication(s) in the second CSI request, configuration of the UE, orbased on other factors determined by the UE).

In some embodiments, this approach for overhead reduction may besomewhat similar to differential CSI feedback where in the number ofbeams required to be reported are split based on their coefficientsalong time domain. The net overhead may be reduced because each timedomain report may require a smaller overhead due to a lower number ofbeams reported in a single report. However only a few kinds of beamsplitting may result in reduced overhead. The UE may also make a choiceto prioritize layers and beams on which it sees stronger energy. Asexplained above, a CSI report for n layers and x beams may be split intotwo reports: one with n layers and k beams first and another with 1layer and x-k beams (across multiple layers). This beam reduction perreport may result in overhead savings. Since PMI may be conditioned onthe rank reported, UE may report two CSIs, both with the same highestrank for a given channel. UE may use a CSI report corresponding to therank 1 for the second report. The performance loss due to the firstreport may be compensated by the subsequent second report which has moreresolution for amplitude and phase for the next few beams.

FIGS. 19-21 —Type II CSI Precoding Overhead Reduction Via LayerPuncturing Across Orthogonal Layers

FIGS. 19-21 illustrate type II CSI precoding overhead reduction vialayer puncturing across orthogonal layers, according to someembodiments. The orthogonality of precoders across layers may beexploited to reduce overhead, e.g., by not reporting some coefficients(e.g., coefficients of some beams may not be reported, e.g., for any/allSBs). For higher ranks, the ideal direction of the beams may be alongright singular vectors of a singular value decomposition (SVD) ofchannel H. Further, a precoder may use beams with right singular vectorsof SVD of angular channel H, e.g., in order to minimize interferencebetween layers. Right singular vectors of H may be the same as the Eigenvectors of a H*H which may not be defective, according to someembodiments. Therefore, the orthogonality of Eigen vectors may be usedfor puncturing layers per each SB. In other words, for each successivelayer, coefficients for one additional beam may be omitted from a CSIreport for all SBs.

FIG. 19 illustrates a type II CSI precoder using layer puncturing acrossorthogonal layers to achieve overhead reduction, according to someembodiments. FIG. 19 is similar to the precoder illustrated in FIG. 11 .However, coefficients for some beams (e.g., over all SBs) are omitted(denoted by an X). It will be appreciated that the use of X in thenotation does not indicate that the omitted coefficients are all thesame (e.g., in many cases, they may be different); X may simply indicatethat the value of these coefficients is omitted from the CSI report.

The number of omitted beams/coefficients may vary with layer. A firstlayer may include (e.g., in a CSI report) coefficients for all beams. Asecond layer may omit one beam. A third layer may omit coefficients fortwo beams, and so on. However, the omitted beams for one layer may bedistinct from the beams omitted for other layers. For example, if afirst beam is omitted from one layer, the first beam may be included forall other layers. It should be noted that the particular coefficientsillustrated as omitted are exemplary only. The beams for whichcoefficients are omitted may be selected in any way (e.g., randomly, byconfiguration of the UE, based on an indication from the base station,set in a standard, based on values of the coefficients (e.g., strongestor weakest), etc.)

The layer puncturing technique may be adopted on top of frequencycompression, e.g., as accepted for study for rank 1-2 UEs. The layerwise orthogonality may be exploited for pre- and post-DFT compression.FIG. 20 illustrates a type II CSI precoder using layer puncturing acrossorthogonal layers to achieve overhead reduction in combination withfrequency compression, according to some embodiments. FIG. 20 is similarto the precoder illustrated in FIG. 19 . However, FIG. 20 furtherillustrates that frequency SB reduction techniques can be appliedindependently. For example, assume the information across N-SBs can beadequately represented by K-taps due to frequency correlation afterfrequency domain compression. Thus, N SBs may be first frequency codedusing DFT and K representative taps may be selected for reporting. Forexample, as shown, compression via layer puncturing may be performed inan N SB basis. Then, frequency compression can be applied in order toreduce to a K DFT basis. Thus, the precoder may be expressed assummations for each of the K taps in the DFT basis, e.g., rather thanthe N SBs of FIG. 19 .

The base station (or receiver of the report) may be configured todetermine the values of the omitted coefficients using the mathematicalproperties of orthogonality, e.g., as shown in FIG. 21 . In other words,the receiver may exploit orthogonality of precoders across layers toreconstruct the missing coefficients (designated by X in FIGS. 19 and 20). The receiver may use the orthogonality of Eigen vectors forpuncturing layers per each SB, e.g., using Gram-SchmidtOrthogonalization. Stated still differently, the receiver may use thesystem of equations to solve for the missing coefficients. Using theexample of FIG. 19 , all coefficients are included for layer 1. Thus,for layer 2 the receiver is able to solve the equations to determine thecoefficients for the omitted beam, X, in layer 2. Each successive layeradds additional equations and additional unknowns so that the set ofequations can be used to solve for all of the unknowns, X, in eachlayer. The layers may thus be solved sequentially. Thus, no complexmechanism is necessary to reconstruct the punctured (e.g., omitted)coefficients at the receiver, according to some embodiments.

FIG. 22 is a table illustrating the bit size of a CSI report using layerpuncturing across orthogonal layers. Precoding with layer puncturingacross orthogonal layers allows for overhead reduction to increase withthe number of layers. Notably, the marginal bit size of the SBcoefficients for each additional layer decreases by 40 bits. Thus, therelative reduction in bit size increases with the number of layers.

The following example may serve to further illustrate Layer wisepuncturing with Gram Schmidt recovery. For transmissions with higherranks {2, 3, 4}, ideal direction of the beams may be along the rightsingular vectors of a SVD channel (H). The right singular vectors mayalso be the Eigen vectors of channel covariance matrix (H*H). Since thecovariance matrix is Hermitian and is bound to be non-defective, theEigen vectors are orthogonal to each other.

For each SB, one or more coefficients in a linear combination of beamsused to specify an Eigen vector (per layer) may be punctured within aCSI report. The orthogonality principle may be utilized at the gnB toreconstruct these punctured coefficients. The puncturing may bereplicated or randomized across different SBs. A gnB may compute thepunctured coefficients using the inner products of the reportedcoefficients. This may increase the computations on the gnB slightly butmay be a simple method to reconstruct the beam directions when number oflayers is more than 1 or spatial multiplexing may be use. In someembodiments, the procedure may not be adopted when the number of layersis 1 which is typically used for beam forming.

Given below may be a typical rank 2 type II SB precoder for i th SB,e.g., according to Release 15:

${W(i)} = \begin{bmatrix}{\begin{bmatrix}\overset{\rightarrow}{b_{0}} & \overset{\rightarrow}{b_{1}} & \overset{\rightarrow}{b_{2}} & \overset{\rightarrow}{b_{3}}\end{bmatrix}\begin{bmatrix}c_{0}^{1} & c_{0}^{2} \\c_{1}^{1} & c_{1}^{2} \\c_{2}^{1} & c_{2}^{2} \\c_{3}^{1} & c_{3}^{2}\end{bmatrix}} \\{\begin{bmatrix}{\overset{\rightarrow}{b}}_{0} & {\overset{\rightarrow}{b}}_{1} & {\overset{\rightarrow}{b}}_{2} & {\overset{\rightarrow}{b}}_{3}\end{bmatrix}\begin{bmatrix}c_{4}^{1} & c_{4}^{2} \\c_{5}^{1} & c_{5}^{2} \\c_{6}^{1} & c_{6}^{2} \\c_{7}^{1} & c_{7}^{2}\end{bmatrix}}\end{bmatrix}$

Where: b_(i) are the same basis, c_(j) ^(i) is the coefficient for the jth beam(j<4) for i th layer across horizontal polarization while c_(j)^(i) is the coefficient for the j th beam(j<4) for i th layer acrossvertical polarization. W(i) is the precoder for i th SB.

After layer puncturing the reported SB precoder may look like:

${W(i)} = \begin{bmatrix}{\begin{bmatrix}\overset{\rightarrow}{b_{0}} & \overset{\rightarrow}{b_{1}} & \overset{\rightarrow}{b_{2}} & \overset{\rightarrow}{b_{3}}\end{bmatrix}\begin{bmatrix}c_{0}^{1} & c_{0}^{2} \\c_{1}^{1} & c_{1}^{2} \\c_{2}^{1} & c_{2}^{2} \\c_{3}^{1} & X\end{bmatrix}} \\{\begin{bmatrix}{\overset{\rightarrow}{b}}_{0} & {\overset{\rightarrow}{b}}_{1} & {\overset{\rightarrow}{b}}_{2} & {\overset{\rightarrow}{b}}_{3}\end{bmatrix}\begin{bmatrix}c_{4}^{1} & c_{4}^{2} \\c_{5}^{1} & c_{5}^{2} \\c_{6}^{1} & c_{6}^{2} \\c_{7}^{1} & c_{7}^{2}\end{bmatrix}}\end{bmatrix}$

Where: X is the punctured coefficient which can take up to 4 bits perSB.

Since the puncturing may be done per layer and may be done per each SB,the net savings may be significant. The layer wise puncturing may be atype of spatial compression where the block diagonal structure of anangularly decomposed channel can be exploited. X may be recovered usingthe equation of FIG. 21 at the gnB. Layer-wise puncturing may be atechnique that scales overhead reduction with the increase in number oflayers.

FIG. 23 —Type II CSI Precoding Overhead Reduction Via Randomized SBCompression

FIG. 23 illustrates a type II CSI precoder using randomized SBcompression to achieve overhead reduction, according to someembodiments. FIG. 23 is similar to the precoders illustrated in FIGS. 11and 19 .

Sparsity in the time domain (e.g., as indicated by channel impulseresponse (CIR), channel energy response (CER), etc.) may be exploited tocompress information in the frequency domain. Thus, a random subset ofSBs may be selected for reporting, and the receiver (e.g., base station)may reconstruct the coefficients using compressed sensing (CS) theoryand concepts. For example, the receiver may use thresholding, optimummatching pursuit (OMP), and/or basis pursuit (BP) to reconstruct omittedcoefficients, among various possibilities. In other words, the receivermay solve for the sparsest solution (e.g., given that there may be moreunknowns than equations, the receiver may perform aminimization/optimization to find the sparsest (e.g., most likely)solution).

A sparse signal of length N (e.g., equal to the number of SBs) with anumber of spikes (e.g., non-zero coefficients) |T| in the time domainmay be exactly reconstructed with O(c*|T|*log N) frequency domainmeasurements using l₁ norm minimization (e.g., convex optimization) withhigh probability. The constant “c” may be independent of N and |T|. Forexample, for a 90% probability of (e.g., exact) reconstruction,typically >8*|T| frequency domain samples may be used, according to someembodiments. In other words, if the number of non-zero time domaincoefficients for a SB is |T|, then 8*|T| total frequency domaincoefficients should be included in the report. A number of SBs to becompressed/omitted may be selected in order to provide 8*|T|coefficients. This may be referred to as providing 8× support. It willbe appreciated that 8× support is exemplary only, and that other levelsof support may be used as desired. For example, higher levels of supportmay be used to improve the probability of exact reconstruction. Lowerlevels of support may be used to further reduce the bit size of the CSIreport.

In some embodiments, an l₁ norm of the signal may also be transmitted bythe UE for faster (e.g., and/or more accurate) reconstruction of thecompressed SBs at the receiver.

In order to encode type II CSI with random SB compression, a wirelessdevice (e.g., a UE) may determine or obtain the CIR/CER at the wirelessdevice. Based on the CIR/CER, the UE may determine the length of support(e.g., number of non-zero time domain coefficients |T|). The UE may thenuse the sparsity/length of support to (e.g., randomly) select a subsetof SBs for reporting CSI. As noted above, the subset may provideapproximately 8× support, among various possibilities.

Note that FIG. 23 illustrates coefficients of some beams being omitted(denoted by X) as discussed above with respect to FIGS. 19-22 . It willbe appreciated that although layer puncturing and randomized SBcompression may be performed in conjunction, that either approach canalso be performed individually.

Further, it will be appreciated that the SB compression illustrated inFIG. 23 is very different than existing techniques of compression in thespatial basis. For example, spatial compression as illustrated in partin FIG. 20 compresses the coefficients from all of the different beamsto a K DFT basis. However, as shown in FIG. 20 , all SBs are still used(e.g., summations from n=0 to N−1). In contrast, in FIG. 23 only asubset of the N SBs are included. Further, spatial compression andfrequency (e.g., randomized SB) compression may be performed inconjunction.

Correlation across different SB coefficients can be used for SBcompression. To exploit the correlation across SBs some transform codingmay reduce the full number of SBs to a given number of principal SBs. Ifthe response is to be reconstructed, additional feedback from the UE maybe useful, e.g., regarding the basis and interpolation parameters. IDFTmay be used to transform the frequency domain channel response to a timedomain response which may be more likely to be sparse due to limitednumber of taps in time domain. However, this may incur loss if theposition of the taps is not accurately estimated and if there is amismatch owing to delays in reporting. Therefore, an approach whichexploits time domain sparsity but which does not rely on accurateestimation of the channel taps may be useful. Also, the time domaincoding may use simultaneous additional processing for each layer at theUE per each layer.

For this approach, random SB compression (e.g., compressed sensing)where the sparsity in time domain response for the channel may beexploited and only coefficients for (e.g., few, uniformly) randomlychosen SBs may be reported to the gnB while trading off with thecomplexity of reconstruction at gnB. Any complex signal made of |T|spikes may be recovered by convex programming by almost every set offrequencies of size O(c|T|log N) where N is the signal length with veryhigh probability.

The response for the remaining SBs may be accurately reconstructed atgnB using convex optimization or basis pursuit approaches with a veryhigh probability. Random SB compression may be sufficient to reconstructa sparse channel.

For example, the algorithm may be developed in the following way: a UEmay use a previously calculated channel impulse response or energyresponse to estimate the sparsity of the channel |T| across each layerand determine the number of frequencies/SBs O(c|T|log N) that arerequired for CSI reporting. The beam coefficients may be sent for theseSBs and the rest of the SBs may be reconstructed at gnB using severalsignal processing techniques available in literature solvable inpolynomial time. This way UE may not need to have a very accuraterepresentation of the channel and an estimate of sparsity is sufficientwhile reporting CSI.

In some embodiments, random SB compression may result in perfectreconstruction of the frequency domain signal.

Further Information and Examples

The following example may further illustrate layer puncturing incombination with frequency compression. As long as N SB information maybe reconstructed from K taps typically by interpolation etc techniques,the orthogonality across layers is preserved across all SBs. To provethis, consider a 2L by R by N SB matrix whose columns are represented byc_(n)r where 1<=r<=R is the layer index and 0<=n<=N−1 is the SB index.Index x represents the number of beams and is irrelevant to thediscussion. By ideal orthogonality across layers we can assume

<{right arrow over (c)}_(n) ^(i)*, {right arrow over (c)}_(n) ^(j)>=0∀i≠j . . .

Also note that:<{right arrow over (c)} _(p) ^(i) *,{right arrow over (c)} _(n) ^(j)>≠0∀i,j∈{1 . . . R}&p,n∈{1 . . . N}  (Equation 1)

We first compute the N-DFT of the SB coefficients for a layer s.

[{right arrow over (c)}₁ ^(s), {right arrow over (c)}₂ ^(s) . . . {rightarrow over (c)}_(N) ^(s)][{right arrow over (W)}₁ {right arrow over(W)}₂ . . . {right arrow over (W)}_(N)]

Where W_(n) are the N-orthogonal DFT basis are represented as below.

$\begin{bmatrix}{\overset{\rightarrow}{W}}_{1} & {\overset{\rightarrow}{W}}_{2} & \ldots & {\overset{\rightarrow}{W}}_{N}\end{bmatrix} = \begin{bmatrix}W_{11} & W_{12} & \ldots & W_{1N} \\W_{21} & W_{22} & \ldots & W_{2N} \\W_{31} & W_{32} & \ldots & W_{3N} \\ \vdots & \vdots & \ldots & \vdots \\W_{N1} & W_{N2} & \ldots & W_{NN}\end{bmatrix}$

From the orthogonality of the columns, one can derive the followingequalities:

$\begin{matrix}{{\begin{bmatrix}W_{11} & W_{12} & \ldots & W_{1N} \\W_{21} & W_{22} & \ldots & W_{2N} \\W_{31} & W_{32} & \ldots & W_{3N} \\ \vdots & \vdots & \ldots & \vdots \\W_{N1} & W_{N2} & \ldots & W_{NN}\end{bmatrix}\begin{bmatrix}W_{11}^{*} & W_{21}^{*} & \ldots & W_{N1}^{*} \\W_{12}^{*} & W_{22}^{*} & \ldots & W_{N2}^{*} \\W_{13}^{*} & W_{23}^{*} & \ldots & W_{N3}^{*} \\ \vdots & \vdots & \ldots & \vdots \\W_{1N}^{*} & W_{2N}^{*} & \ldots & W_{NN}^{*}\end{bmatrix}} = I_{N}} & \left( {{Equation}2} \right)\end{matrix}$ $\begin{matrix}{{\sum\limits_{n = 0}^{n = {N - 1}}{❘W_{in}❘}^{2}} = 1} & {{\forall i} = {\left\{ {1,{2\ldots N}} \right\}.}}\end{matrix}$

The cross product terms:

$\begin{matrix}\begin{matrix}{{\sum\limits_{n = 0}^{n = {N - 1}}{W_{in}{W_{jn}}^{2}}} = 0} & {{\forall i},{j = \left\{ {1,{2\ldots N}} \right\}},{i \neq j}}\end{matrix} & \left( {{Equation}3} \right)\end{matrix}$

Now the pre-coder after frequency compression can be written as:

${\begin{bmatrix}{\overset{\rightarrow}{c}}_{1}^{1} & {\overset{\rightarrow}{c}}_{2}^{1} & \ldots & {\overset{\rightarrow}{c}}_{N}^{1} \\{\overset{\rightarrow}{c}}_{1}^{2} & {\overset{\rightarrow}{c}}_{1}^{2} & \ldots & {\overset{\rightarrow}{c}}_{1}^{2} \\ \vdots & \vdots & \ldots & \vdots \\{\overset{\rightarrow}{c}}_{1}^{R} & {\overset{\rightarrow}{c}}_{2}^{R} & \ldots & {\overset{\rightarrow}{c}}_{N}^{R}\end{bmatrix}\begin{bmatrix}W_{11} & W_{12} & \ldots & W_{1N} \\W_{21} & W_{22} & \ldots & W_{2N} \\W_{31} & W_{32} & \ldots & W_{3N} \\ \vdots & \vdots & \ldots & \vdots \\W_{N1} & W_{N2} & \ldots & W_{NN}\end{bmatrix}} = \begin{bmatrix}{\sum\limits_{x = 0}^{N - 1}{W_{x1}{\overset{\rightarrow}{c}}_{x}^{1}}} & {\sum\limits_{x = 0}^{N - 1}{W_{x2}{\overset{\rightarrow}{c}}_{x}^{1}}} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}{\overset{\rightarrow}{c}}_{x}^{1}}} \\{\sum\limits_{x = 0}^{N - 1}{W_{x1}{\overset{\rightarrow}{c}}_{x}^{2}}} & {\sum\limits_{x = 0}^{N - 1}{W_{x2}{\overset{\rightarrow}{c}}_{x}^{2}}} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}{\overset{\rightarrow}{c}}_{x}^{2}}} \\ \vdots & \vdots & \ldots & \vdots \\{\sum\limits_{x = 0}^{N - 1}{W_{x1}{\overset{\rightarrow}{c}}_{x}^{R}}} & {\sum\limits_{x = 0}^{N - 1}{W_{x2}{\overset{\rightarrow}{c}}_{x}^{R}}} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}{\overset{\rightarrow}{c}}_{x}^{R}}}\end{bmatrix}$

Consider the inner product across layers (rows i,j nth term):

$\begin{matrix}{< {\left( {\sum\limits_{x = 0}^{N - 1}{W_{xn}{\overset{\rightarrow}{c}}_{x}^{i}}} \right)^{H}\left( {\sum\limits_{y = 0}^{N - 1}{W_{yn}{\overset{\rightarrow}{c}}_{y}^{j}}} \right)} > {\forall{i \neq j}}} \\{\left. \Rightarrow{{❘W_{xn}❘}^{2} < {\overset{\rightarrow}{c}}_{x}^{i^{H}}} \right.,{{\overset{\rightarrow}{c}}_{x}^{i} > {+ {\sum\limits_{{y = 0},{\forall{x \neq y}}}^{N - 1}{W_{yn}{\sum\limits_{x = 0}^{N - 1}W_{xn}^{*}}}}} < {\overset{\rightarrow}{c}}_{x}^{i^{H}}},{{\overset{\rightarrow}{c}}_{y}^{i} >}}\end{matrix}$

First term goes to zero from orthogonality assumptions across layersfrom Equation 1 leaving the residual:

${{\sum\limits_{{y = 0},{\forall{x \neq y}}}^{N - 1}{W_{yn}{\sum\limits_{x = 0}^{N - 1}W_{xn}^{*}}}} < {\overset{\rightarrow}{c}}_{x}^{i^{H}}},{{\overset{\rightarrow}{c}}_{y}^{i} >}$

Now adding the terms across N coefficients SBs (columns of the pre-codedmatrix) and considering Equation 3 above:

${\sum\limits_{n = 0}^{N - 1}\left( {{{\sum\limits_{y = 0}^{N - 1}{W_{yn}{\sum\limits_{x = 0}^{N - 1}W_{xn}^{*}}}} < {\overset{\rightarrow}{c}}_{x}^{i^{H}}},{{\overset{\rightarrow}{c}}_{y}^{j} >}} \right)} = 0$

Therefore, as long as the DFT basis vectors are orthogonal and sameacross all layers, orthogonality across layers may be exploited. If UEselects a set of K representative taps enabling frequency compressionfor reporting some interpolation may be done at the gNB to recover allfrequency SBs. In some embodiments, all N taps may be available at gNBafter interpolation, etc.

In order to perform layer domain compression, prior to selecting K tapspuncture one coefficient incrementally across all taps, the precodingmatrix may look like:

$\begin{bmatrix}{{\sum\limits_{x = 0}^{N - 1}{W_{x1}{\overset{\rightarrow}{c}}_{x}^{1}}},} & {\sum\limits_{x = 0}^{N - 1}{W_{x2}{\overset{\rightarrow}{c}}_{x}^{1}}} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}{\overset{\rightarrow}{c}}_{x}^{1}}} \\{{\sum\limits_{x = 0}^{N - 1}{W_{x1}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{2} \\0\end{bmatrix}}},} & {\sum\limits_{x = 0}^{N - 1}{W_{x2}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{2} \\0\end{bmatrix}}} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{2} \\0\end{bmatrix}}} \\ \vdots & \vdots & \ldots & \vdots \\{{\sum\limits_{x = 0}^{N - 1}{W_{x1}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{R} \\ \vdots \\0\end{bmatrix}}},} & {{\sum\limits_{x = 0}^{N - 1}{W_{x2}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{R} \\ \vdots \\0\end{bmatrix}}},} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{R} \\ \vdots \\0\end{bmatrix}}}\end{bmatrix}$

At the gNB, the zeros may be interpreted as unknowns. Interpolationfollowed by Inverse DFT is performed and subsequently equation (1) maybe applied to recover the missing coefficients. As seen above a UE mayincrementally zero out a beam coefficient across N SBs for a given layerprior to DFT compression, this may automatically reduce the size of theprecoder from 2L×K coefficients to (2L−1)×K with savings K*(3 to 4bits).

$\begin{bmatrix}{{\sum\limits_{x = 0}^{N - 1}{W_{x1}{\overset{\rightarrow}{c}}_{x}^{1}}},} & {\sum\limits_{x = 0}^{N - 1}{W_{x2}{\overset{\rightarrow}{c}}_{x}^{1}}} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}{\overset{\rightarrow}{c}}_{x}^{1}}} \\{{\sum\limits_{x = 0}^{N - 1}{W_{x1}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{2} \\0\end{bmatrix}}},} & {\sum\limits_{x = 0}^{N - 1}{W_{x2}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{2} \\0\end{bmatrix}}} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{2} \\0\end{bmatrix}}} \\ \vdots & \vdots & \ldots & \vdots \\{{\sum\limits_{x = 0}^{N - 1}{W_{x1}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{R} \\ \vdots \\0\end{bmatrix}}},} & {{\sum\limits_{x = 0}^{N - 1}{W_{x2}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{R} \\ \vdots \\0\end{bmatrix}}},} & \ldots & {\sum\limits_{x = 0}^{N - 1}{W_{xN}\begin{bmatrix}{\overset{\rightarrow}{c}}_{x({1:{{2L} - 1}})}^{R} \\ \vdots \\0\end{bmatrix}}}\end{bmatrix}{\begin{bmatrix}W_{11}^{*} & W_{21}^{*} & \ldots & W_{N1}^{*} \\W_{12}^{*} & W_{22}^{*} & \ldots & W_{N2}^{*} \\W_{13}^{*} & W_{23}^{*} & \ldots & W_{N3}^{*} \\ \vdots & \vdots & \ldots & \vdots \\W_{1N}^{*} & W_{2N}^{*} & \ldots & W_{NN}^{*}\end{bmatrix}}$

The gNB can recover the missing coefficients across each SB by applyingorthogonality post DFT decompression using equation (1) and solving forX₁:

$\begin{matrix}\begin{bmatrix}{\overset{\rightarrow}{c}}_{1}^{1} & {\overset{\rightarrow}{c}}_{2}^{1} & \ldots & {\overset{\rightarrow}{c}}_{N}^{1} \\\begin{bmatrix}{\overset{\rightarrow}{c}}_{1{({1:{{2L} - 1}})}}^{r} \\X_{1}\end{bmatrix} & \begin{bmatrix}{\overset{\rightarrow}{c}}_{1{({1:{{2L} - 1}})}}^{r} \\X_{2}\end{bmatrix} & \ldots & \begin{bmatrix}{\overset{\rightarrow}{c}}_{1{({1:{{2L} - 1}})}}^{r} \\X_{k}\end{bmatrix} \\ \vdots & \vdots & \ldots & \vdots \end{bmatrix} \\\begin{matrix}{{< {\overset{\rightarrow}{c}}_{n}^{i^{*}}},{\begin{bmatrix}{\overset{\rightarrow}{c}}_{1{({1:{{2L} - 1}})}}^{r} \\X_{1}\end{bmatrix}>=0}} & {\forall{i \neq j}}\end{matrix}\end{matrix}$

Thus, frequency compression and layer puncturing may be applied incombination as illustrated in FIG. 20 .

In the following, exemplary embodiments are provided.

In some embodiments, a user equipment device (UE) may comprise: a radio;and a processing element operably coupled to the at least one radio andconfigured to cause the UE to: establish a connection with a basestation; receive, from the base station, control information forreporting channel state information; perform one or more measurements;determine a method of encoding the channel state information withreduced overhead; generate, based on the one or more measurements andthe method of encoding, at least one channel state information report;and transmit the at least one channel state information report to thebase station.

In some embodiments, the method of encoding may comprise beam splitting,wherein at least one channel state information report includes a firstreport and a second report.

In some embodiments, the control information may specify a plurality oflayers, wherein the first report includes each of the number of layers,wherein the second report includes only one of the number layers.

In some embodiments, the first report and the second report may eachindicate a same rank, wherein the same rank is based on the number oflayers.

In some embodiments, the control information may specify a plurality ofbeams, wherein the plurality of beams includes a number, x, of beams,wherein the first report includes a subset, k, of the plurality ofbeams, wherein the subset, k, of the plurality of beams includes the kstrongest beams of the plurality of beams, wherein the second reportincludes x-k beams weaker than the k strongest beams.

In some embodiments, an apparatus for reporting channel stateinformation of a user equipment device (UE), may comprise: a processingelement configured to cause the UE to: establish a connection with abase station; receive, from the base station, control information,wherein the control information specifies: a plurality of layersincluding 3 or more layers; a plurality of L beams; and a plurality of Nsubbands; perform channel state measurements; dynamically select, basedat least in part on the control information, at least one technique forreducing overhead associated with reporting channel state information;encode, based on the channel state measurements and the at least onetechnique for reducing overhead, a channel state information report; andtransmit the channel state information report to the base station.

In some embodiments, the at least one technique for reducing overheadassociated with reporting channel state information may include layerpuncturing across orthogonal layers, wherein the channel stateinformation report excludes coefficients for each subband of theplurality of N subbands for at least one beam of the plurality of Lbeams for at least one layer of the plurality of layers.

In some embodiments, the channel state information report includescoefficients for each subband of the plurality of N subbands for eachbeam of the plurality of L beams for a first layer of the plurality oflayers, wherein the channel state information report excludescoefficients for each subband of the plurality of N subbands for onebeam of the plurality of L beams for a second layer of the plurality oflayers, wherein the channel state information report excludescoefficients for each subband of the plurality of N subbands for twobeams of the plurality of L beams for a third layer of the number oflayers.

In some embodiments, the one beam of the plurality of L beams may bedistinct from the two beams of the plurality of L beams.

In some embodiments, the at least one technique for reducing overheadassociated with reporting channel state information further includesrandomized subband compression.

In some embodiments, the at least one technique for reducing overheadassociated with reporting channel state information may includerandomized subband compression, wherein the processing element isfurther configured to cause the UE to: randomly select a subset of theplurality of N subbands to include in the channel state informationreport.

In some embodiments, the processing element may be further configured tocause the UE to: exclude, from the channel state information report, allsubbands that are not part of the subset.

In some embodiments, the channel state measurements include at least oneof: channel impulse response (CIR); or channel energy response (CER),wherein the processing element is further configured to cause the UE to:determine the size of the subset based on the at least one of the CIR orCER.

In some embodiments, the processing element may be further configured tocause the UE to: transmit an 11 norm associated with the channel stateinformation report to the base station.

In some embodiments, a method for managing a base station may comprise:at the base station: establishing a connection with a user equipmentdevice (UE); transmitting, to the UE, control information for reportingchannel state information, wherein the control information specifies: atleast one technique for reducing overhead associated with reportingchannel state information; a plurality of layers including 3 or morelayers; a plurality of L beams; and a plurality of N subbands;receiving, from the UE, a first channel state information reportaccording to the control information, wherein the channel stateinformation report omits at least one coefficient; and interpreting thefirst channel state information report according to the at least onetechnique for reducing overhead associated with reporting channel stateinformation.

In some embodiments, the at least one technique for reducing overheadassociated with reporting channel state information may include beamsplitting, wherein the method further comprises: receiving, from the UE,a second channel state information report according to the controlinformation, wherein the second channel state information reportincludes a higher spatial resolution than a first spatial resolution ofthe first channel state information report.

In some embodiments, the first channel state information report may bereceived at a first time and the second channel state information reportis received at a second time, wherein said interpreting may includeusing the higher spatial resolution of the second report to approximatethe at least one coefficient.

In some embodiments, the at least one technique for reducing overheadassociated with reporting channel state information may include layerpuncturing across orthogonal layers, wherein said interpreting includesusing the orthogonality of Eigen vectors to solve a system of equationsfor the at least one coefficient.

In some embodiments, said interpreting may include sequentially solvingsystems of equations for at least a subset of the plurality of layers.

In some embodiments, the at least one technique for reducing overheadassociated with reporting channel state information may includerandomized subband compression, wherein said interpreting includesreconstructing the at least one coefficient using at least one of:thresholding; optimum matching pursuit (OMP); or basis pursuit (BP).

Another exemplary embodiment may include a wireless device, comprising:an antenna; a radio coupled to the antenna; and a processing elementoperably coupled to the radio, wherein the device is configured toimplement any or all parts of the preceding examples.

A further exemplary set of embodiments may include a non-transitorycomputer accessible memory medium comprising program instructions which,when executed at a device, cause the device to implement any or allparts of any of the preceding examples.

A still further exemplary set of embodiments may include a computerprogram comprising instructions for performing any or all parts of anyof the preceding examples.

Yet another exemplary set of embodiments may include an apparatuscomprising means for performing any or all of the elements of any of thepreceding examples.

Yet another exemplary set of embodiments may include a 5G NR networknode or base station configured to perform any action or combination ofactions as substantially described herein in the Detailed Descriptionand/or Figures.

Yet another exemplary set of embodiments may include a 5G NR networknode or base station that includes any component or combination ofcomponents as described herein in the Detailed Description and/orFigures as included in a mobile device.

Embodiments of the present disclosure may be realized in any of variousforms. For example, some embodiments may be realized as acomputer-implemented method, a computer-readable memory medium, or acomputer system. Other embodiments may be realized using one or morecustom-designed hardware devices such as ASICs. Still other embodimentsmay be realized using one or more programmable hardware elements such asFPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of the methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a device (e.g., a UE 106) may be configured toinclude a processor (or a set of processors) and a memory medium, wherethe memory medium stores program instructions, where the processor isconfigured to read and execute the program instructions from the memorymedium, where the program instructions are executable to implement anyof the various method embodiments described herein (or, any combinationof the method embodiments described herein, or, any subset of any of themethod embodiments described herein, or, any combination of suchsubsets). The device may be realized in any of various forms.

It is well understood that the use of personally identifiableinformation should follow privacy policies and practices that aregenerally recognized as meeting or exceeding industry or governmentalrequirements for maintaining the privacy of users. In particular,personally identifiable information data should be managed and handledso as to minimize risks of unintentional or unauthorized access or use,and the nature of authorized use should be clearly indicated to users.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. An apparatus, comprising: a processor configuredto cause a user equipment device (UE) to: establish a connection with abase station; receive, from the base station, control information forreporting channel state information, wherein the control informationspecifies: a technique for channel state information reporting, whereinthe technique includes omitting certain coefficients in reporting; aplurality of layers including 3 or more layers; a plurality of L beams;and a plurality of N subbands; determine a plurality of coefficients forthe reporting according to the technique; and transmit, to the basestation, a first channel state information report according to thecontrol information, wherein the first channel state information reportomits at least one coefficient of the plurality of coefficients.
 2. Theapparatus of claim 1, wherein the technique includes a reduction ofcoefficients in a frequency domain.
 3. The apparatus of claim 1, whereinthe technique includes a reduction of coefficients for at least onelayer of the plurality of layers.
 4. The apparatus of claim 1, whereinthe technique includes a reduction of coefficients for at least one beamof the plurality of L beams.
 5. The apparatus of claim 1, wherein thetechnique includes beam splitting, wherein the processor is furtherconfigured to cause the UE to: transmit, to the base station, a secondchannel state information report according to the control information,wherein the second channel state information report includes a higherspatial resolution than a first spatial resolution of the first channelstate information report.
 6. The apparatus of claim 1, wherein thetechnique includes layer puncturing across orthogonal layers, whereinthe first channel state information report excludes coefficients foreach subband of the plurality of N subbands for at least one beam of theplurality of L beams for at least one layer of the plurality of layers.7. The apparatus of claim 1, wherein the technique includes excluding atleast one subband.
 8. An apparatus, comprising: a processor configuredto cause a user equipment device (UE) to: establish a connection with abase station; receive, from the base station, control information forreporting channel state information, wherein the control informationspecifies: a technique for channel state information reporting, whereinthe technique includes compression; a plurality of layers including 3 ormore layers; a plurality of L beams; and a plurality of N subbands;determine a plurality of coefficients for reporting according to thetechnique; and transmit, to the base station, a first channel stateinformation report according to the control information, wherein thefirst channel state information report omits at least one coefficient ofthe plurality of coefficients.
 9. The apparatus of claim 8, wherein thetechnique includes selecting a subset of the plurality of N subbands.10. The apparatus of claim 9, wherein the subset of the plurality of Nsubbands is selected randomly.
 11. The apparatus of claim 9, wherein thetechnique includes omitting all coefficients for respective subbands ofthe subset of the plurality of N subbands.
 12. The apparatus of claim 9,wherein a number of respective subbands of the subset of the pluralityof N subbands is based on a number of non-zero coefficients in a timedomain.
 13. The apparatus of claim 9, wherein the subset of theplurality of N subbands is selected based at least in part on at leastone of: a channel impulse response (CIR); or a channel energy response(CER).
 14. The apparatus of claim 8, wherein the technique includestransmitting an l₁ norm.
 15. An apparatus, comprising: a processorconfigured to cause a base station to: establish a connection with auser equipment device (UE); transmit, to the UE, control information forreporting channel state information, wherein the control informationspecifies: a technique for channel state information reporting, whereinthe technique includes omitting certain coefficients in reporting; aplurality of layers including 3 or more layers; a plurality of L beams;and a plurality of N subbands; and receive, from the UE, a first channelstate information report according to the control information, whereinthe first channel state information report omits at least onecoefficient of a plurality of coefficients.
 16. The apparatus of claim15, wherein the technique includes a reduction of coefficients in afrequency domain.
 17. The apparatus of claim 15, wherein the techniqueincludes a reduction of coefficients for at least one layer of theplurality of layers.
 18. The apparatus of claim 15, wherein thetechnique includes a reduction of coefficients for at least one beam ofthe plurality of L beams.
 19. The apparatus of claim 15, wherein thetechnique includes beam splitting, wherein the processor is furtherconfigured to cause the UE to: transmit, to the base station, a secondchannel state information report according to the control information,wherein the second channel state information report includes a higherspatial resolution than a first spatial resolution of the first channelstate information report.
 20. The apparatus of claim 15, wherein thetechnique includes layer puncturing across orthogonal layers, whereinthe first channel state information report excludes coefficients foreach subband of the plurality of N subbands for at least one beam of theplurality of L beams for at least one layer of the plurality of layers.